This invention relates generally to optical scanners, and more particularly to optical scanners for providing a digital representation of three dimensional objects.
Methods for successfully obtaining two dimensional (xe2x80x9c2-Dxe2x80x9d) color image data for objects have been developed. This process is commonly known as two dimensional scanning or digitizing. When an object is scanned, a digital data file is created which contains image data including color information which is associated with a set of two dimensional points or coordinates. The color information is obtained by an optical detector or set of optical detectors that are typically organized in a one or two dimensional array.
Matching the color information with the correct two dimensional point or location is not a significant problem in two dimensional scanning since the two dimensional point on which the optical detector is focused is the same point that is associated with the color information obtained by the detector. The color information is mislocated only to the extent that there is some error in the location of the point on which the detector is focused (e.g. an error introduced by the optical system) and that error can readily be minimized.
The problem of associating color information with three dimensional (xe2x80x9c3-Dxe2x80x9d) objects is not so easily solved. This is because prior art methods obtain color information with a two dimensional scanning method, while position information is obtained by a three dimensional scanning method. The mapping of the 2-D color information to the 3-D position information is a complicated process which is prone to significant error.
Many methods exist for obtaining the three dimensional location of the surface points of the object. One such method is a system which uses a laser range finder to scan the object and record the distance between the known three dimensional location of the range finder and the measured location of the surface of the object. The result of using this method or other methods of generating three dimensional surface models is a set of three dimensional points which accurately represent the surface of the object. A characteristic of this method and other methods of obtaining a three dimensional surface model is that it is inherently monochromatic, that is, no color information is obtained in the process. If three dimensional color information is desired, then it must be generated by somehow combining or conformally mapping the two dimensional color information onto the three dimensional surface model.
The problem of conformally mapping the two dimensional color information onto the three dimensional surface model is difficult and it is common for mismatching of color information with the three dimensional points to occur. The problem may be visualized by imagining a white statue or bust of a person""s bead and a color photograph of the same person""s face. The photograph cannot simply be projected onto the bust to transfer the correct color information to the correct points on the bust or significant distortion will occur. A significant amount of judgment must be exercised in order to correctly associate the color information from the photograph with the correct surface points on the bust. Similarly, it is difficult to accurately associate color information obtained from two dimensional optical detectors with the correct points on a three dimensional surface model. Another problem in the prior art is that color information is not used to determine surface locations, which means less than the total amount of information that is available is being used. Furthermore, both a 2-D and 3-D system is required, which adds cost.
What is needed is a way of generating a set of three dimensional points representing a surface in such way that the three dimensional points are already associated with color data so that conformally mapping separately generated color data onto the set of three dimensional surface points is not necessary. Furthermore, it is desirable to utilize all available frequencies of light to determine surface point positions to maximize the accuracy of the scanning process and to eliminate a separate 3-D scanning step.
Accordingly, the present invention provides a system and method for using the color information from a series of two dimensional color images to derive the three dimensional location in space of the surface points which produced the color images. Because the color information itself is used to derive the three dimensional location of the surface points, there is no need to conformally map separately generated color information onto the derived three dimensional surface points. The points are derived from color information and so are already associated with the correct color information. Also, the use of the color information increases the accuracy of the three dimensional location of the surface points.
In one embodiment, the present invention provides a three dimensional digital scanner which includes a multiple view detector which is responsive to a broad spectrum of visible light. The multiple view detector is operative to develop a plurality of images of a three dimensional object which is being scanned. The plurality of images are taken from a plurality of relative angles with respect to the object, and the plurality of images depict a plurality of surface portions of the object. A digital processor including a computational unit is coupled to the detector and is responsive to the plurality of images so that it develops 3-D coordinate positions and related image information for the plurality of surface portions of the object. A three dimensional image of the object to be scanned is thus developed by the digital processor. The data developed includes both shape and surface image color information.
In another embodiment, a three dimensional color digital scanner includes a color detector responsive to a broad spectrum of visible light to develop a plurality of images of a three dimensional object. A rotary object support having an axis of rotation allows the detector to develop a plurality of images of a three dimensional object. The plurality of images depict a plurality of surface portions of the object. A digital computer is coupled to the detector. The computer tracks patches of the surface portions of the object to determine coordinates of the patches as a function of the rotation of the rotary object support and determines radii of the patches from the axis of rotation.
In another embodiment, a method for scanning a three dimensional object includes developing a plurality of images of a three dimensional object taken from a plurality of relative angles with respect to the object. The plurality of images depict a plurality of surface portions of the object to be scanned. 3-D coordinate positions and related image information about the plurality of surface portions of the object is computed from the plurality of images such that a three dimensional image of the object is developed that includes both shape and surface image information.
In another embodiment, a method for determining three dimensional coordinates of a surface portion of an object includes obtaining a plurality of images of the surface portion of the object and identifying a trackable patch of the surface portion in an initial image. An initial set of two dimensional coordinates of the trackable patch in the initial image is determined along with at least one additional set of two dimensional coordinates of the trackable patch in another of the images. A radial coordinate of the trackable patch is determined and then a set of three dimensional coordinates of the trackable patch are determined from the radial coordinate of the trackable patch.
In another embodiment, a method for determining three dimensional coordinates of a surface portion of an object includes rotating the object about an axis of rotation so that a plurality of images of the surface portion of the object are obtained as the object is rotates about the axis of rotation. A trackable patch is identified and the two dimensional coordinates of the trackable patch are determined. The movement of the trackable patch is tracked as a function of the rotation of the object. A radial distance of the trackable patch from the axis of rotation is determined based on the movement of the trackable patch as a function of the rotation of the object and three dimensional coordinates of the surface portion of the object are derived from the coordinates of the trackable patch and the radial distance of the trackable patch from the axis of rotation.
The present inventions provides a system and method for obtaining 3-D surface information that is linked to color information without the need to conformally map 2-D color data onto a 3-D surface. The accuracy of the system is enhanced by the use of color data and the cost of the system is reduced because the 3-D surface is derived from a series of 2-D images. These and other advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings.